He's become a successful CEO and a generous person, but ten years ago, Facebook CEO Mark Zuckerberg used to have something of an attitude.

For example, he used to carry a business card that read, "I'm CEO...Bitch."

Once, back then, Zuckerberg played a pretty nasty prank on top venture capital firm Sequoia Capital.

It was 2004, and Zuckerberg still wasn't convinced that he wanted to run Facebook forever. He thought maybe another startup idea of his, called Wirehog, would be a bigger success.

So he was out talking to venture capitalists about raising money.

Sequoia Capital reached out to him.

Zuckerberg had no intention of considering an investment from Sequoia. That's because Zuckerberg had hired, and become friends with, Napster co-founder Sean Parker. Sequoia had invested in Parker's startup Plaxo, and it hadn't gone well. There was bad blood.

But even though there was no way Zuckerberg was going to take Sequoia money, he took the meeting anyway. He had a prank in mind.

There were three elements to it:

First, Zuckerberg showed up intentionally late to the 8 a.m. meeting.

Second, he showed up late wearing ... pajamas.

Third, Zuckerberg walked to the front of the room and presented a PowerPoint deck titled "The Top Ten Reasons You Should Not Invest."

In the style of David Letterman, he began to tick his way down the list.

Some of those reasons:

"We have no revenue."

"We will probably get sued by the music industry."

"We showed up at your office late in our pajamas."

"Because Sean Parker is involved."

"We're only here because [a Sequoia partner] told us to come."

Obviously, Sequoia did not invest in Wirehog.

It never invested in Facebook either.

Even by 2010, Zuckerberg felt bad about the prank. He told David Kirkpatrick, author of "The Facebook Effect," "I assume we really offended them and now I feel really bad about that."

Yesterday, Zuckerberg made amends.

Yesterday, Facebook announced that it would acquire messaging startup WhatsApp for $19 billion.

Guess who was WhatsApp's sole venture investor -- according to Forbes, owner of about 40% of the company?

Sequoia Capital.

The firm Mark Zuckerberg pranked when he was a kid will make about $6.4 billion dollars on the deal.